I have no intention of belittling the incident, but I fail to see how shutting everything down is a proper response to any incident of less than catastrophic scale.

I take that back, I can see a reason: CYA. Nobody would want to be the one who makes the decision to keep the metro system running and have a second attack occur. I'm still not convinced that CYA is a sufficient reason, however.

If you don't shut down and an second and/or third incident then happens in a coordinated attack, it's very easy to say "Why didn't you shut down? Couldn't you see that we were under attack?"

That's "what's the point of using acronyms when you can just write out the full sentence?"

Well, you could ask the National Aeronautics and Space Administration, the Central Intelligence Agency, or even consult with the Massachusetts Institute of Technology. Perhaps you can send them JavaScript Object Notation using the Asynchronous Javscript and Extensible Markup Language standard over HyperText Transfer Protocol?

</s>

I use acronyms to reduce the cognitive overhead of reading, and (relevant to this discussion) make otherwise offensive terms acceptable in a broad range of environments (snafu, CYA, OMFG, WTF, etc). I'm sorry you haven't run across CYA before (though that might be a good thing), but it's not a terribly uncommon acronym either.

Regular old inclement weather does this all the time and people don't cry panic that society is going to implode.

Shutting down transportation for a day is a silly thing to be terrorized about.

>As for us, we behave like a herd of deer. When they flee from the huntsman's feathers in affright, which way do they turn? What haven of safety do they make for? Why, they rush upon the nets! And thus they perish by confounding what they should fear with that wherein no danger lies. . . . Not death or pain is to be feared, but the fear of death or pain. Well said the poet therefore:—Death has no terror; only a Death of shame!

-Epictetus